Optical fiber probe for optical coherence tomography with extended depth of field using a modified GRIN fiber lens

We present a new modified graded-index (GRIN) fiber lens for extending the depth of field (DOF) of a miniature optical fiber probe for optical coherence tomography (OCT). The index profile of the GRIN fiber is designed to extend the DOF by 2X using a single piece of the GRIN fiber lens while maintaining an outside diameter of 125 μm. The output beam profiles of the optical fiber probe made with such GRIN fiber lens are measured and found to be in good agreement with the theoretical simulation.